Chlorofluorocarbon compounds (CFCs) and hydrochlorofluorocarbon compounds (HCFCs) as a class possess unique chemical stability and solvent properties and have until only recently been used in a wide variety of applications. Among other applications, CFCs have found utility in drying processes, cleaning processes (e.g., the removal of flux residues from printed circuit boards), and vapor degreasing applications. Many CFCs, CFC-113 particularly, possess a valuable combination of solvency, non-flammability, and low toxicity, that make them ideally suited for many challenging solvent cleaning applications. But while these materials were initially believed to be environmentally benign, they now are linked to ozone depletion. According to the Montreal Protocol and its attendant amendments, production and use of CFCs must be discontinued (see, e.g. P. S. Zurer, Looming Ban on Production of CFCs, Halons Spurs Switch to Substitutes, CHEM. & ENG'G NEWS, Nov. 15, 1993, at 12).
Many performance characteristics are sought in CFC and HCFC replacements. Such replacements typically are required to possess low ozone depletion potential, low flammability, and low toxicity, and to have boiling point ranges that are suitable for a variety of solvent cleaning applications. Ideal replacement solvents also have the ability to dissolve both hydrocarbon-based and fluorocarbon-based soils.
There remain, however, solvent cleaning applications that require solvent characteristics not optimally possessed by any one replacement material. Among the most challenging solvent cleaning applications is the requirement of a solvent or solvent blend material that is non-flammable under conditions of cleaning and that exhibits a requisite solvency toward silicones and other difficulty-dissolved contaminant materials (e.g., hydraulic fluids and the like). These solvent compositions must also be compatible with (i.e., not act aggressively toward) protective coatings and plastic parts.